Monday, March 21, 2011

Isn't Nature Great?

Have you ever been watching a wildlife programme on TV and thought to yourself "Why don't zebras have better camouflage if nature is so smart?" You'll have noticed that they stand out a mile on the great plains of Africa.  Well, the fact is that their stripes aren't meant to be the usual sort of camouflage that blends in with their surroundings.  A predator, let's say a lioness, will approach a herd of zebra in an attempt to panic them, making them run so that she can pick out a weak individual. The herd will run, but to the lion's eyes the zebras' stripes blend together to form a great amorphous mass, making isolating an individual animal very difficult. Not for nothing is a group of zebras called a "dazzle."

Lions themselves have an interesting adaptation. Examine a close-up photo of a lions face and you will see a distinct white line under it's eyes. Being predominantly nocturnal hunters this gives the big cat an added advantage over it's prey in the pitch black African night. This white line reflects any ambient light from the stars or moon into the lion's eyes enhancing it's night vision.  Prey animals like the impala for example don't have this, so while they can smell danger as the lion approaches in the dark they are unable to see it. imagine how terrifying that must be. The lion of course can see the impala as though it were wearing night-vision goggles.

You will often see prey animals such as impala or wildebeest approach a predator like a lion when they have spotted it.  This isn't as stupid as it might seem.  Many predators use ambush as their primary means of catching prey. The prey animal will be quite relaxed as long as it can see the predator. It knows it can out-run and out-turn a predator in order to escape. Once the predator disappears from view however, the prey animal will become very nervous.  It can be fascinating to watch lions hunting as a pride. It's as if they use telepathy to get into position. You'll see the pride watching a herd of wildebeest, seemingly quite relaxed and uninterested when as if at some unheard signal they suddenly become alert and move into hunting mode. Some of the pride will crouch and begin slinking through the grass, circling around behind the wildebeest herd, where they will hide in the undergrowth, superbly camouflaged by their tawny coats. At another silent signal other lions who have remained behind will charge at the wildebeest herd, panicking them and making them run........straight into the ambush set by the lions crouching in the long grass. It is an incredible thing to watch such a lion hunt develop.

Rhino's too have some interesting behaviour patterns.  White (or wide mouthed) rhinos heads are held much lower than their Black (or hook lipped) cousins. This is because they are grazers, they eat grass. Black rhinos are browsers and eats shrubs and leaves hanging from low trees. You are more likely to encounter white rhinos in open ground and for this reason an alarmed female with a calf will always run away behind it's calf in order to protect it's rear. The black rhino is more often found in scrubby areas and an alarmed mother will run ahead of her calf in order to clear a path through the undergrowth.

I think perhaps my favourite adaptation from the natural world is that of the flat-topped acacia thorn tree of the Masai Mara and the Serengeti. These trees will allow giraffes to feed on them for just so long before sending out chemical messages to other trees in the immediate vicinity warning them that they are under attack. The trees then begin to produce extra tannin which the giraffe's find distasteful and so wander off to find another group of trees to feed on - and so it goes on. The animals get a feed but don't decimate the trees. It's all wonderfully sustainable. I just love nature. 

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